Route planning devices are well known in the field of navigational instruments. The method of route planning implemented by known prior art systems depends on the capabilities of system resources, such as processor speed and the amount and speed of memory. As increased system capability also increases system cost, the method of route planning implemented by a navigation device is a function of overall system cost.
One feature of increased system capability involves detour route calculation capabilities. Many conventional navigational devices simply do not incorporate a detour route calculation functionality in order to reduce system complexity and maintain a low overall system cost. Some of these devices may alert the user that they are off course when the user makes a detour, but they do not perform any course or route recalculation to accommodate for the intended or unintended detour in route. The intended or unintended detour can be for reasons such as thoroughfare conditions, thoroughfare congestion (e.g. rush hour or road construction), check point delays and the like. Some navigational devices include functionality which allows the device to calculate a new route based on an in route decision to avoid one or more thoroughfares, or sections, of a planned route. However, these devices require the user to point to, highlight, or draw a box around the segment which the user wants to avoid. That is, the decision to calculate a new route is not dynamically tied to the current route on which the user is traveling. Requiring the user to point to, highlight, or draw a box around the segment which the user wants to avoid is also distracting to do while the user is driving or trying to navigate the route.
In conventional navigational methods and devices the user may have to halt their journey in an attempt to decide upon a new route, or course, and must rely on traditional navigational methods, e.g. asking directions, following detour signs (in the case of a forced detour) or using a conventional map. In some devices, the user may still be able to see the previously planned route, but they will have to employ their own decision making to chart themselves around that portion of the previous route they want to avoid and yet still be headed toward a desired destination. This can be time consuming and provide frustration to a user who is likely unfamiliar with the routes surrounding their current location.
Clearly, in many cases halting travel to decide upon a new route is not a viable alternative. For example, when the user is traveling on an interstate it is entirely impossible to simply stop. The alternative of pulling off on the shoulder is undesirable and can be dangerous. Stopping travel is equally undesirable since doing so increases travel time and provides an added inconvenience to the user. In other instances, such as navigating downtown city streets, the traffic issues alone may prevent the user from stopping their vehicle to decide upon a new route. As mentioned above, even if the user has the ability to safely stop their vehicle, such as when traveling in a neighborhood, the inconvenience factor is present.
Another problem is that when a device is used to perform a new route calculation from a new position (off of the originally planned route) to a desired destination, the calculation is not going to take into account the reason for the intended or unintended detour. As a result, the new route calculation will often provide a route which includes travel on the thoroughfare from which the detour was taken. Thus, the new route does not provide any solution to the need for avoiding the thoroughfare from which the detour was taken. As the reader will appreciate the intended or unintended detour may be for reasons of traffic congestion, road construction, the type of thoroughfare, and the like.
In summary, current prior art systems have created a spectrum of products in which the degree of navigational accuracy is dictated primarily by the cost of the system. The lower cost systems currently offer a low degree of accuracy and functionality that is often inadequate for users. Therefore, there exists a need for a navigational route planning device which is more efficient and accurate than current low cost systems, without requiring more expensive system resources. In addition, there is also a need for a navigational route planning device which provides a user with more dynamic route calculation capabilities.